1. INTRODUCTION
Pollinators are important agents for a stable ecosystem (Kremer, 2008; De Groot et al., 2010). They enhance pollination for both wild and flowering plants and also help humans to increase agricultural production (Kevan et al., 1990; Corbet et al., 1991; Widhiono et al., 2016). These insects also benefit the economic, aesthetic, and cultural aspects of mankind (Gill et al., 2016). In general, social and solitary bees, butterflies and moths, beetle and flies account as dominant pollinators (Vanbergen and Initiative, 2013; Wojcik, 2021).
Most of the cultivated plants around the world are pollinated by bees (56.5%), flies (19%) and, butterflies (4%) (Bashir et al., 2019). Honey bees are well–known insects in comparison to wild pollen bees (Losey and Vaughan, 2006; Potts et al., 2010) while flies and butterflies are less known. (Jennersten, 1984; Larson et al., 2001). Pollinators decline is a globally recorded phenomenon (Carvalheiro et al., 2013; Dirzo et al., 2016). Especially, bumblebees (Fitzpatrick et al., 2007; Cameron et al., 2011), butterflies (Warren et al., 2001; Van Swaay et al., 2010), and honeybees (Vanengelsdrop et al., 2008) population is shrinking in the world due to natural as well anthropogenic threats. The major drivers of pollinator loss are recognized as habitat loss, landscape modification, intensification in agriculture, and even climate change (Kearns et al., 1998; Potts et al., 2010; Kovács‐Hostyánszk et al., 2017). Hence, maintaining pollinator diversity in the given landscape requires an understanding of a clear pattern of pollinator diversity along with the habitat types.
The community composition of pollinators depends upon the local environment (Williams et al., 2010). The activity of pollinators is strongly correlated with air temperature; bees and butterflies prefer warmer temperatures than flies (Kühsel & Blüthgen, 2015), plant species richness (Hudewenz et al., 2012), and elevation; Hymenoptera is dominant pollinators in lowland while Lepidoptera and Diptera dominate at high land (Warren et al., 1988). They require a range of habitats for fulfilling their ecological requirements. However, these ecological demands for insect pollinators are mostly species or guild–specific (Proesmans et al., 2019). Bees prefer to forage the flower plants close to the nesting area (Gathmann and Tscharntke, 2002; Greenleaf et al., 2007). Hoverflies and butterflies do not construct the nest and fly away from the egg–laying areas for foraging. Aphidophagous hoverflies such as Episyrphus , Sphaerophoria depend on agricultural habitat (Jauker et al., 2009; Pinheiro et al., 2015), while saproxylic hoverflies (Xylota ) are benefitted from the forest (Reemer, 2005), hence, strongly associated with them. Butterflies forage varieties of flower for nectar (Tiple et al., 2005) and can make the flight over greater distances (Herrera, 1987). Such movement may show the selection of varied nutrition of butterflies; pollen (Gilbert, 1972), tree sap, rotting fruit, and dung, decaying flesh, and dissolved minerals in wet sand or dirt. Additionally, oviposition–plant location signifies habitat selection for smaller and less mobile butterflies, such as the ”blues,” while the larger butterflies like Erebia epipsodea and Colias probably have fairly large ranges of the search for their widespread ovipositing plants (Sharp et al., 1974). Bee’s community structure is also designated by the availability of the nesting substrates. Bee species construct the nest in deadwood (Sydenham et al., 2016) and in the soil of sun–exposed ground (Everaars et al., 2011). So, habitat sharing among the pollinators is obvious. The habitat types play a crucial role in the community composition, abundance, diversity, and species richness of flowering plants and hence the pollinators.
Few studies were found on the study of insect pollinators in different habitats of National Park. We hypothesized that the visit of insect pollinators depends on the floral diversity found in the given habitats. The presence of these plants is strongly influenced by habitat types and elevation. The general understanding is that the natural habitat, if free from pesticides, will probably possess more diversity than the managed habitat. However, the habitat heterogeneity would also affect the pollinator community as the interaction plant–pollinator is specific (Weibull et al., 2000; Rundlöf et al., 2008; Oliver et al., 2010).
Similarly, we examined species richness, abundance and, the community composition of insect pollinators in different habitats along the elevation gradient. The pollinator survey was carried at Shivapuri–National Park (SNNP) including managed habitats of buffer zone areas. The research questions were designed to find whether the pollinator composition (richness, abundance, and their association) differs from the defined habitats (grassland, managed area, open trails, and trails of forest) of SNNP. ‘Is pollinator composition influenced by the elevation gradient at the landscape?’